A photolithography process may be a general process for forming a pattern. In the photolithography process, a predetermined pattern of a photomask may be transferred into a photoresist film on a wafer, and then an underlying layer may be etched according to a photoresist pattern. Such a photolithography process may have an affect on fineness and/or integration degree of a circuit in the fabrication of electronic devices such as a semiconductor memory device, an integrated circuit device, a TFT LCD, etc.
In a photolithography process, a photoresist film may be formed on a wafer by coating with a photoresist material. The photoresist film may be exposed to light by projecting a pattern of a photomask or a reticle with an exposure apparatus, and then the photoresist film may be developed to form a photoresist pattern having a desired image. The wafer or an underlying layer may be etched using the photoresist pattern as an etching mask. An ion implantation process may be performed on a wafer or a structure on a wafer using the photoresist pattern as a mask. The photoresist pattern may be removed from a substrate by ashing or stripping.
A variety of light sources may be used in the photolithography process. For example, the light source of the exposure process may be a C-line, an I-line, KrF, ArF, ultraviolet radiation, electron beam, X-ray, etc. The G-line has a relatively long wavelength, and the X-ray has a relative short wavelength.
The photoresist film may be formed using a photoresist material that is sensitive to light having a specific wavelength. The photoresist material may have components (e.g., resin, photosensitive agent, additives, etc.) that may be dependent on the type of light sources. When chemical structures of the resin or photosensitive agents vary, physical or chemical properties (e.g., sensitivity to light, etch-resistance, stripping property, solubility in solvent) of the photoresist material also may also vary largely.
In a photolithography process, a thinner composition is a material used for removing a photoresist or diluting a photoresist, due to its ability to dissolve photoresist. The dissolving ability of the thinner composition may depend on the chemical composition of the thinner and/or components of a photoresist to be dissolved. The commercial thinner composition may dissolve a specific type of photoresist, but may not have good ability to dissolve various types of photoresist, since various types of photoresist generally have substantially different chemical compositions.
As an integration degree and/or pattern density of a semiconductor device increases, usage of a wafer having a large diameter also increases. The large wafer may be rinsed while rotating at a relatively slow speed. The wafer may shake at the slow rotational speed. Thus, the thinner composition having a poor or improper dissolving rate for photoresist may not uniformly remove edge beads of photoresist.